1. Field of the invention
The present invention relates to the field of preparing baths for the processing of photographic materials. The invention further relates to a manifold adapted for separating liquid and gas. The invention still further relates to a use of the manifold for preparing a processing bath.
The invention addresses the field of preparing or replenishing baths of liquids in applications, where there is a need to avoid gas bubbles and foam in the bath, and where there is a desire to minimize agitation of the body of liquid held in the bath. Such concerns arise in applications with liquids prone to enter undesired reactions with air, where air locks may form, and/or where agitation in the liquid may give rise to uncontrolled variations in the processing conditions. These considerations may have particular importance in connection with liquids containing surfactants that enhance their propensity to form foam and bubbles.
One field of application, where these considerations apply, is the field of baths for photographic processing.
The processing solutions or development liquids used are in many cases highly reactive and very likely to react with substances in the air, e.g. with oxygen. The development liquids may also comprise tensides or other surfactants including them to foam formation. The surfactants are important for furthering desirable properties of the processing solutions, e.g. for making the liquids effective towards dissolving and stripping off non-exposed areas of emulsion within a photographic piece of material.
However, surfactants make processing solutions susceptible to foam formation on pumping and agitation, as may occur during replenishment of the tank. The foam may clog vents and pipes and may cause spill over. Problems with excessive foam formation may lead to the decision to avoid the surfactants, thus forgoing their desirable capabilities in other aspects.
2. Description of the Prior Art
U.S. Pat. No. 5,309,191 describes an apparatus adapted for replenishment and flushing of a tank which forms part of a photographic processing apparatus. The apparatus comprises replenishment tanks, a manifold, a pump, and valves for permitting controlled introduction of processing solution into a tank. The inlet for the processing solution is at the bottom of the tank with the view to avoid air from being entrapped in the processing apparatus.
Feeding in liquid at the bottom of the tank requires the establishment of a fluid conduit, which is inherently open to undesirable backflow into the feed piping, e.g. during time intervals when the feed pump is stopped. The risk of backflow may be encountered, e.g. by the installation of active means, such as check valves.
However, for considerations of safety and reliability it would be preferred to have a system where the prevention of backflow would not need to rely on the performance of active means.
Feeding in liquids through a manifold placed below the liquid surface level makes it complicated to maintain complete separation between different ingredients intended to be mixed in the bath. This is a concern since the ingredients, when in a concentrated state, may be susceptible to enter undesirable reactions among them, e.g. to form gel. Feeding in liquid at the lower portion of the tank does not completely avoid the risk of introducing air bubbles since the feed pipe may occasionally suck in air, e.g. during a phase when the replenishment tank is being emptied.
U.S. Pat. No. 5,622,545 discloses a separator for removing gases from water for the purpose of treating water for fish aqua cultures. The separator comprises a vortex tube wherein water is injected to spin downwardly while gas may exit the separator through a gas exit port at the top.
U.S. Pat. No. 3,044,236 discloses a system for removal of gases from liquids in order to prepare gas-free samples from chemical process streams prior to their analyses. The system comprises a gas disengager, wherein a gas-liquid mixture is introduced tangentially with the purpose of stripping away any gas. A weir serves to limit variations in hydrostatic head.